Glass compositions



metal oxides.

United States Patent Office 3,095,311 Patented June 25, 1963 3,095,311 GLASS COMPOSITIONS Guido von Wranau, Plainfield, and Charles J. Phillips, New Brunswick, N.J., assignors of to said Von Wranau, to said Phillips, W to Thomas T. Chappell, Cedar Knolls, to Raymond J. Lamb, Ridgewood, 9, to H. Curtis Meanor, Glen Ridge, and W to Walter A. Sproule, Rutherford, NJ.

No Drawing. Filed June 29, 1960, Ser. No. 39,462 13 Claims. (Cl. 106-50) This invention relates to glass compositions suitable for the manufacture of glass products requiring extremely high chemical stability, for instance, glass fibers and pharmaceutical containers, and it also relates to the glass products themselves, as well as to a method of drawing glass fibers.

As far as .compositions for glass products of high chemical stability are concerned, commonly used glasses, such as soda-lime glasses, are unsuited. Fibers, for instance, when made of such glasses, are not resistant to the dissolving action of the atmosphere. They show poor chemical durability and corrode quickly. Yet, in the case of textiles, when made of glass fibers, high resistance to atmospheric conditions is an unconditional requirement.

There was the belief that it is the alkali in common glasses, that is dissolved by water adsorbed from the atmosphere and, thus, is the reason for poor chemical durability, and various suggestions were, therefore, made for alkali-free glasses or glasses practically free of alkali, to be used for the attenuation of fibers, which suggestions were directed toward substituting boron oxide for alkali In fact, bo-rosilicate type glasses have found wide use in fiber attenuation. However, while the compositions used satisfy the requirements for insol-ubility and electrical insulation, they have the disadvantage of requiring very high temperatures to melt and to achieve the iluidity needed for fining the glass mass.

A known fiber glass composition is formulated as follows:

Percent sio 52 to 56 A1203 to CaO 16 to 19 B203 9 t0 MgO 3 to 6 The drawing or fiber-forming range of this composition lies well above 2400 R, and its melting temperature lies still higher. It will be appreciated that such temperatures, in combination with the chemical attack, have a most destructive effect on the refractories. In addition, the high temperatures required would be injurious to the attenuating bushings unless they are made of platinum. Thus, according to a known glass fiber-drawing process in actual use, according to which little balls (marbles) of glass are made first and are then, upon inspection for impurities and prior to the drawing of the fibers, remelted, the remelting is done in a furnace made completely of platinum.

The following is an example of a widely used borosilicate composition, referred to hereinafter for comparison and explanatory purposes as prior composition:

The use of compositions of the above given two formulations and of similar formulations is not fully satisfactory inasmuch as these compositions require a large investment in platinum for the furnaces and attenuating bushings, necessitate extremely careful control of the temperatures at the spinnerets, and are destructive to the refractories.

The primary object of the present invention is to provide glass products of high chemical stability and to generally improve glasses to be used for the manufacture of such products.

A more specific and important object of our invention is to provide glass compositions which may be melted and formed into fibers at temperatures which will be less injurious to the furnace refractories and will not require spinnerets made of platinum and which, at the same time, have very high chemical durability.

Further objects of this invention center about glass formulations which will allow the formation of fibers not only at lower temperatures than up to now but also over a relatively wide operating range, making sure that the temperature control will not be too critical, and which will be resistant to devitrification. By operating range is meant the temperature limits at which the bushings in the fiberizing apparatus must be maintained. The temperature limits correspond approximately to viscosities from log 2 to log 3, i.e. from 100 to 1000 poises. By devitrification resistance is meant the tendency to retain the high viscosity at the l-iquidus temperature to provide for effective attenuation of fibers without, however, the danger of crystallization.

An extensive program of experimentation, resting on numerous series of widely varying compositions, has led us to low-alkali lime-alumin-o-silcates showing a substantial decrease of the boron oxide content, as compared with the known borosilicates, and the presence of certain addition agents. The glasses we have discovered do not have the disadvantage of the borosilicates so fiar used for the attenuation of fibers, but will embody all the commercially desired advantages, such as low melting and fiberforming temperatures, a sufliciently wide operating range, the yield of a fiber of good corrosion resistance, high chemical durability, good electrical insulating properties, and good devitrification resistance.

The glasses of our invention lie within the following ranges in percentages by weight:

; Percent SiO 40 to 59 A1 0 7 to 17 CaO 9 to '24 PhD 0 to 11 ZnO 0 to 11 BaO 0 to 5 MgO 0 to 5 CaF 0 to 3 B203 0 t0 6 0 t0 7 Zl'Oz 0 t0 4 L1 0 1 to 4 Na o 0 to 2 K 0 0 to 6 The limits as given 'hereinbefore of the constituents of our compositions have been determined by compounding batches within and including these limits and determining that the melting temperature (temperature in the melting zone) does not exceed 2450 F. and is mostly considerably lower, that the fiber-forming temperatures vary between approximately 2000 F. and 2450 F., and that the chemical durability with respect to water varies between about .014 and 049% of loss in weight.

It is to be noted that the durability tests were made by melting the compositions into a disk about 2" in diameter and A" in thickness. The disk was then crushed into a powder that passed a 50 mesh screen and did not Composi- Prior comtlon 9 position Melting temp, viscosity log 2, F 2, 385 2, 810 Fiber-drawing temp, viscosity log 2-3, F. 2020-2385 2370-2810 Solubility in water, percent .026 .048 Solubility in H01 percent 870 1.200

It will be appreciated that the melting and fiber-forming temperatures of our compositions are lower than the respective temperature of the prior composition or the known compositions, and that the chemical durability of the present composition is greater. The melting and fiber-forming temperatures, the working ranges, and chemical resistance to water are indicated for each of the specific compositions listed hereinafter. And it will be apparent that the compositions of our invention, when compared with the prior composition, have about the same silica content, a considerably decreased boron oxide content, and various added agents.

In working with compositions according to the invention and testing the fiber-drawing properties of individual compositions, we observed certain important regularities. Thus, the combined amounts of SiO and A1 0 vary between approximately 55 and 66 percent, which means that neither the combined lower limit quantities nor the combined upper limit quantities of both SiO and A1 0 would ensure satisfactory results.

Similarly, the combined quantities of CaO, PbO, ZnO, BaO, and MgO amount to a range from about 19 to 31 percent. In this connection, it should be noted that CaO alone could largely satisfy this requirement and, therefore, could be used alone, omitting all or any combinations or any one of the lead, zinc, barium, and magnesium oxides, but it has been found that Zn and/ or Mg improves the resistance to devitrification.

TiO and ZrO increase the resistance to solubilizing influences. If titanium dioxide is omitted, the solubility doubles and triples. Zirconium dioxide acts similarly as does TiO but to a lesser degree. Also, Zr0 tends to raise the melting temperature of the batch.

B 0 is a useful flux which lowers the melting point. Li O, Na O, and K 0 are important, making the glass melt easily.

Out of Li O, Na O, and K 0, we prefer to use simultaneously at least two of the three alkali oxides. As can be seen from the foregoing general formulation of our composition, Li O is present in every case.

We have further found that if two glasses are compared for chemical durability, and these two glasses are substantially identical in composition, except that the first glass has, for instance, 1.0% Na O and 3.0% U 0, and the second glass 0.8% Na O and 1.9% Li O, the first will be 50% more durable than the second despite its much higher alkali content.

It should be noted that it has been known for a long time that a ratio of 2.0 to 2.5 times more K 0 than Na O gives better durability than any other proportion, but it now appears that, with the same total amount of alkali oxides, the presence of Li O ensures better durability than any combination of Na O and K 0.

If the amounts of some of the hereinbefore referred to addition agents, namely TiO Z102, Li O, Na O, and K 0, are increased or decreased so that they will be out- 4. side the limits indicated, then either the chemical durability or the fiber-drawing temperature or both will be radically changed.

The following compositions are examples of formulations which have been found satisfactory:

Compositions Total, percent 100. 0 100.0 100.0 Loss of weight in 1120 test, percent.-." .014 .019 .010 Melting temperature, F 2, 400 2, 400 2, 400

From these three compositions it will be seen that if all other constituents remain substantially constant, the amounts of Si0 and A1 0 may vary considerably without appreciably influencing the chemical durability in water, as long as the total amount of SiO and A1 0 remains constant. Thus, in Compositions 2 and 3 SiO; and A1 0 difier, but the total of SiO,-; and A1 0 is 61.3% in each case, and the loss in weight is likewise the same in each case, namely, .019%. This loss is weight is somewhat greater than for Composition 1 since the total of SiO and A1 0 which is 63.3% in Composition, is slightly less in Compositions 2 and 3.

Compositions Percent:

48. 3 43. 5 48. 0 11. 5 l6. 0 11.0 14.0 14. 0 l4. 0 10.0 10.0 10.0 1. 0 l. O 1. 0 1. 0 1. 0 1. 0 2. 0 2. 0 2.0 2.0 2. O 2.0 4.0 4.0 4.0 1. 0 1. 0 1.0 1. 6 0.5 3. (i 5.0 6. 0

Total, percent 100.0 100.0 100.0 Loss of weight in Water, percent .024 .02 .024 Melting temperature, F 2, 425 2, 400 2, 425

In glasses having substantially the same total of SiO and A1 0 and being otherwise identically composed, except for Na O and K 0, the relative amounts of Na O and K 0 may vary considerably without affecting the chemical durability in water, as can clearly be seen from Compositions 4, 5 and 6.

Composition 3 is here repeated to demonstrate that Compositions 3, 7 and 8 show that in glasses of similar compositions, with SiQ plus A1 being held substantially constant, omission of PhD and the replacement thereof by substantially equal amounts of either CaO or CaO plus BaO cause an increased loss of weight in water, although the glasses of Compositions 7 and 8 are still to be regarded as absolutely very durable.

A comparison between repeated Composition 7 and Composition 9 shows that an increase in total alkali may actually decrease the loss of weight in a water durability test, provided a substantial amount of the alkali is present in the form of Li O, and the other constituents are properly proportioned. This effect was not to be expected since it was the presence of alkali constituents, as has already been stated, that was regarded to be largely responsible forloss in weight in water durability tests.

The presence of Li O also lowers the upper and lower limits of the worklng temperature.

Compositions Percent: I

310 52.3 48.3 4.83 13. 0 ll. 0 15. 0 14. 0 l4. 0 14. 0 10. 0 10. 0 10. 0 1. 0 l. 0 1. 0 1. 0 1. 0 1. 0 1. 0 2. 0 2. 0 2. 0 4. 9 4. 9 4. 0 1. 9 1. 9 1. 9 -0. 8 0. 8 0. 8 2. 0 2. 0 2. 0

Total, percent; 100. 0 100. 0 100. 0 Loss in weight in 1110 test, percen 049 .018 014 Melting temperature, F 2, 450 2, 430 2, 400

Compositions 10, 11 and 12 are interesting in showing that in glasses of similar compositions the use of small amounts of T102 decreases the loss of weight in a water durability test substantially.

Compositions Percent:

O 40.0 59. 0 AlzO 15.0 7.0 B103. 6. 0 4. 0 C210 20.0 9.0 PbO 11.0 ZnO 11.0 MgO 'IiOv 6 0 3.0 Z102- 3. 0 L110 l 0 1.0 Nero l 0 2.0

Total, percent 100.0 100.0

Loss of weight; in 11 0 test, percent .029 Melting temperature, F 2,350 2,350

Loss of Loss of weight in weight in H30 5% 11 Cl test Compositions according to the present invention, inc. 10% P 014-. 024 40-. 60 Present compositions without PbO 026-. 049 44-. 88 "Prior composition 041-. 055 1.20 Soda-lime window glass 164 Thus, it appears that our glass is better in chemical durability than one of the best of the known fiber glass compositions, the predominantly used composition and,

of course, very much better than soda-lime window glass.

It is believed that the features and advantages of our invention will be clear from the foregoing. It will be seen that our novel glass compositions melt at lower temperatures than known compositions, that they can be attenuated at lower temperatures, and that they yield a fiber of high chemical durability. In every other respect, our fiber is as satisfactory as known fibers. While from the prior composition fibers can be drawn at approximately 15,000 f.p.m. when the glass temperature is 2475 F., our fibers can be drawn at the same speed at 2125 F. or a temperature 350 F. lower.

It will be apparent that while we have described a number of formulations of the glass composition of our invention, many changes and modifications may be made without departing from the spirit of the invention defined in the appended claims.

We claim:

1. Glass consisting essentially of the combined amounts of Li O, Na o and K 0 varying between 2 and 7%.

2. In the glass according to claim 1, the combined amounts of SiO and A1 0 varying between approximately 55 and 66 percent.

3. In the glass according to claim 1, the combined amounts of CaO, PbO, ZnO, Ba-O, and MgO varying between approximately 19 and 31 percent.

4. The glass according to claim 1, wherein, out of CaO, PbO, ZnO, BaO and MgO, CaO is present beside at least one of the oxides ZnO and MgO.

5. The glass according to claim 1, wherein, out of Li O, Na O, and K 0, Li O is present beside at least one of the oxides Na O and K 0.

7 6. A glass consisting essentially of Percent Si 48.3 A1 0 15.0 CaO 14.0 PbO 10.0 ZnO 1.0 MgO 1.0 CaF 2.0 T 4.0 Li O 1.9 Nazo 0.8 K 0 2.0

7. A glass consisting essentially of Percent SiO 48.3 A1 0 11.5 CaO 14.0 PbO 10.0 ZnO 1.0 MgO 1.0 CaF 2.0 B 0 2.0 TiO 4.0 Li O 1.0 N820 K 0 3.6

8. A glass consisting essentially of Percent S10 48.0 A1 0 11.0 CaO 14.0 PbO 10.0 ZnO 1.0 MgO 1.0 CaF 2.0 B 0 2.0

TiO 4.0 Li O 1.0 K 0 6.0

9. A glass consisting essentially of Percent Si0 48.3 A1 0 13.0 CaO 22.0

ZnO 2.0 MgO 1.0 CaF 3.0 B 0 2.0 TiO 4.0 Li O 1.9 Na O 0.8 K 0 2.0

10. A glass consisting essentially of Percent SiO 51.0 A1 0 11.0 CaO 20.0 ZnO 3.0 1.0

MgO

Percent Ca'F 1.0 B 0 2.0 TiO 4.0 Li O 3.0 Na O 1.0 K 0 2.0

11. A glass consisting essentially of Percent SiO 48.3 A1 0 11.0 CaO 14.0 PbO 10.0 ZnO 1.0 MgO 1.0 CaF 2.0 B 0 4.0 Ti0 4.0 Li O 1.9 Na O 0.8 K 0 2.0

12. In the manufacture of glass fibers, the method which includes melting SiO 40% to 59%, A1 0 7% to 17%, C210 9% to 24%, PhD 0% to 11%, ZnO 0% to 11%, BaO 0% to 5%, MgO 0% to 5%, Ca-F 0% to 3%, B 0 0% to 6%, Ti0 0% to 7%, ZrO 0% to 4%, Li O 1% to 4%, Na O 0% to 2%, K 0 0% to 6%, the combined amounts of Li O, Na O and K 0 varying between 2 and 7%, and drawing fibers from the molten glass thus obtained at a temperature varying between approximately 2000 F. and 2450 F., the logarithm of viscosity at said temperatures equaling 3 and 2, respectively.

13. Glass fibers consisting essentially of the combined amounts of Li O, Na O and K 0 varying between 2 and 7%.

References Cited in the file of this patent UNITED STATES PATENTS 2,334,961 Schoenlaub Nov. 23, 1943 2,571,074 Trede et a1 Oct. 9, 1 951 2,664,359 Dingledy Dec. 29, 1953 2,877,124 Welsch Mar. 10, 1959 

13. GLASS FIBERS CONSISTING ESSENTIALLY OF PERCENT SIO2 40 TO 59 AL203 7 TO 17 CAO 9 TO 24 PBO 0 TO 11 ZNO 0 TO 11 BAO 0 TO 5 MGO 0 TO 5 CAF2 0 TO 3 B203 0 TO 6 TIO2 0 TO 7 ZRO2 0 TO 4 LI2O 1 TO 4 NA20 0 TO 4 K20 0 TO 6 THE COMBINED AMOUNTS OF LI2O, NA2O AND K2O VARYING BETWEEN 2 AND 7%. 